The proposed studies will investigate differences in cardiovascular and in autonomic reactivity between adolsecent black and white students at risk for later development of hypertension. Subjects will be between 18 and 21 years of age. One hundred forty-four college males will be stratified by ethnic group, positive (or negative) family history of hypertension and by mean blood pressure value obtained on an initial screen. Other variables to be collected include height, weight, hematocrit and skin fold thickness. To evaluate behavioral/psychlogical factors and their relationship to cardiovascular responsivity one session will be devoted to interviews and behavioral/psychological stressors. Interviews will focus on college stress and coping behaviors anger, and a structured interview to classify the subject as Type A/B. In order to evaluate mental and psychomotor stress, mental arithmetic, digit substitution and tapping will be performed. In order to evaluate interpersonal interactions at a variety of stress levels a video game that is programable will be used so that level of interpersonal competition can be modified. On a second study day, response to the physiologic challenges of tilt, cold and treadmill exercise will be evaluated. These studies will give insight into differences in reactivity between black and white subjects. From an understanding of the differences in black-white reactivity and the influence of prior blood pressure and family history, we expect to better understand the relevancy of reactivity differences to the higher incidence of hypertension in black persons.